Method and apparatus for front-lit semi-retro-reflective display

ABSTRACT

The disclosure generally relates to a front-lit display having transparent and selectively emissive light directionality. The disclosed semi-retro-reflective, semi-specular and specular displays include directional front light systems that reflect light in a manner to preserve the non-Lambertian characteristic of the light output. This leads to brighter displays with a higher degree of luminance as compared to conventional microencapsulated electrophoretic displays with substantially Lambertian reflectance where much of the light is not reflected back towards the viewer.

The instant application is a continuation application of applicationSer. No. 14/500,737, filed Sep. 29, 2014, which claimed the filing datepriority to the filing date of Provisional Application No. 61/884,854,filed Sep. 30, 2013; the specification of all the foregoing applicationsare incorporated herein in their entirety.

FIELD

The disclosure relates to front-lit, semi-retro-reflective displays andmethods for manufacturing thereof. In one embodiment, the disclosurerelates to a front-lit display having transparent and selectivelyemissive light directionality.

BACKGROUND

Conventional front-lit illuminated microencapsulated electrophoreticdisplays characteristically reflect light in the white state in aso-called Lambertian manner. The light originating from a front light isradiated equally in all directions with equal luminance in the whitestate. Thus, a large portion of the reflected light is not reflectedback to the viewer thereby limiting the perceived brightness of thedisplay. This is inefficient by about a factor of two, of the perceivedluminance to screen exitance where about 50% of the light is reflectedaway from the viewer.

The light output is different with conventional rear illuminated LCDdisplays where the emitted light is largely confined to approximately a30° half-angle cone centered around a direction perpendicular to theplane of the front light. The illuminated LCD displays approximatelydoubles the ratio of perceived luminance to screen exitance for typicalviewing angles. This roughly doubles the battery life. That is, theratio of the ratio of perceived luminance to screen exitance increasesfrom lip, the value for Lambertian light, to roughly 2/p.

Therefore, in order for broader adoption of reflective displays by thepublic, there is a need for an improved front-lit, reflective displayshaving an increased ratio of perceived luminance to exitance which leadsto a brighter display.

BRIEF DESCRIPTION OF DRAWINGS

These and other embodiments of the disclosure will be discussed withreference to the following exemplary and non-limiting illustrations, inwhich like elements are numbered similarly, and where:

FIG. 1A schematically illustrates a conventional microencapsulatedelectrophoretic type display showing Lambertian reflectance in the whitestate;

FIG. 1B schematically illustrates a conventional frustratable TIRdisplay with light being substantially reflected back to the viewer in asemi-retro-reflective manner in the white state;

FIG. 2 illustrates a frustratable TIR semi-retro-reflective displayaccording to one embodiment of the disclosure;

FIG. 3 is a close-up view of light being reflected off the extractorelements within the light guide of a directional front light system in asemi-retro-reflective TIR display;

FIG. 4 illustrates an exemplary display according to another embodimentof the disclosure;

FIG. 5 illustrates an exemplary embodiment of the disclosure having aperforated sheet;

FIG. 6 illustrates an exemplary embodiment of the disclosure having aperforated sheet and a conductive specularly reflective layer; and

FIG. 7 illustrates an exemplary embodiment of the disclosure having aperforated sheet with a reflective layer.

DETAILED DESCRIPTION

FIG. 1A schematically illustrates a conventional microencapsulatedelectrophoretic type display showing Lambertian reflectance in the whitestate. Specifically, FIG. 1 shows display 10 having a layer ofmicrocapsules 12 containing light absorbing black particles 15 and lightreflecting particles 14. Display 10 is shown in the white or reflectivestate where light reflecting particles 14 are located at the outwardsurface of display 10 towards viewer 16. Conventional light reflectingparticles include Titanium Dioxide (TiO₂).

An incident light beam depicted by dotted ray 18 is shown where the beamis nearly perpendicular to the outward surface of display 10. The lightis reflected in all directions in a Lambertian manner as depicted by themultiple light reflection rays 20. As shown in FIG. 1A, a substantialamount of light is not reflected back to the viewer 16.

FIG. 1B schematically illustrates a conventional frustratable TIRdisplay with light being substantially reflected back to the viewer in asemi-retro-reflective manner in the white state. Specifically, FIG. 1Bshows a frustratable total internal reflection (TIR) display 50 with ahemispherical beaded front sheet 52. Such displays are disclosed, forexample, in U.S. Pat. No. 6,885,496 B2. Display 52 is in the light statewhen it reflects light in a semi-retro-reflective manner back to viewer54. An incident light beam depicted by dotted ray 56 in a directionnearly perpendicular to the front surface 52 is reflected back to theviewer 54. When light is reflected in a semi-retro-reflective manner (orin a semi-specular manner), as depicted by reflected light rays 58, asubstantial portion of the light is reflected back to the viewer 54. Asa result the display has a higher degree of luminance and may appearbrighter to the viewer.

In one embodiment, the disclosure relates to a display with: (a) a frontlight that is mainly transparent and selectively emits lightdirectionally at a perpendicular direction relative to the surface ofthe outward sheet of the display, and (b) a reflective electronic papersurface that has less diffusive characteristic including semi-specularor semi-retro-reflective so as to substantially preserve thenon-Lambertian characteristic of the light output in order to maximizethe ratio of luminance to exitance. In one embodiment, FIG. 3 showsroughly how light source and light guides work where the light sourceinjects light in a parallel direction to the surface of the outwardsheet of the display and into the light guide wherein the light guidethen re-directs it in a perpendicular direction to the surface of theoutward sheet of the display.

In certain embodiments, the disclosure relates to a display formed froma combination of a front light and a reflective electronic papersurface. In an exemplary embodiment, the front light is configured todirectionally emit light in a perpendicular direction within a narrowangle with respect to a the plane perpendicular to the outward surfaceof the display.

Conventionally, specular reflection is defined as the mirror-likereflection of light from a surface in which light from a single incomingdirection (i.e., a ray) is reflected into a single outgoing direction.This behavior is described by the law of reflection, which states thatthe direction of incoming light (incident ray), and the direction ofoutgoing light reflected (reflected ray) make the same angle withrespect to the surface normal. That is, the angle of incidence equalsthe angle of reflection and that the incident, normal, and reflecteddirections are coplanar. In one embodiment of the disclosure, theelectronic paper surface is semi-specular or semi-retro-reflective wherethe reflection maintains high brightness but has a whiter or softerappearance to the viewer.

A combination of a front-lit, transparent surface, that is lessdiffusive (i.e. more specular) provides a display that reflects lightand preserves the non-Lambertian output of the front light sourceleading to a brighter display.

FIG. 2 illustrates a frustratable TIR semi-retro-reflective displayaccording to one embodiment of the disclosure. Display 100 of FIG. 2 isequipped with a directional front light system. Display 100 includes asemi-retro-reflective front sheet 102 having a plurality of partiallyembedded high refractive index transparent convex protrusions. Theconvex protrusions may be of varying design and shape depending on theapplication. In FIG. 2 the convex protrusions are in the shape ofhemispherical beads 104 that extended inwardly. The display in FIG. 2 isfurther comprised of a transparent front electrode 106 on the inwardsurface of the hemispherical beads 104 and a rear support 108 equippedwith a rear electrode 110. Rear electrode 110 may comprise a thin filmtransistor (TFT) array or a patterned electrode array.

Display 100 is also shown with voltage source 112 which connects frontelectrode 106 to rear electrode 110. Contained within the cavity formedby front electrode 106 and rear electrode 110 is an inert, lowrefractive index medium 114. Medium 114 may contain suspendedelectrophoretically mobile particles 116.

Display 100 may further include a directional front light systemequipped with light source 118, light guide 120 and array of lightextractor elements 122. In one embodiment, the front light source may becomprised of, but not limited to, a light emitting diode (LED), coldcathode fluorescent lamp (CCFL) or a surface mount technology (SMT)incandescent lamp.

The light guide directs light to the front entire surface of sheet 102while the light extractor elements direct the light in a perpendiculardirection towards the outward surface of the semi-retro-reflective sheet102. It should be noted that the light guide comprising of extractorelements 122 illustrated in FIG. 2 is a conceptual drawing. Inconventional light guide systems the extractor elements may be, but notlimited to, embedded reflective elements or air pockets, wherein thereflection is caused by the mismatch of refractive index values at theinterface between the light guide polymer material and the air pocket.Additionally, the size and location of the extractor elements may varyso as to cause a uniform extraction of the light. For all drawingsherein that comprise a light guide system, the light guide system shownis intended to be illustrative for conceptual purposes only.

On the left side of the dotted line 126, display 100 shows a portion (ora pixel) of the display in the white or semi-retro-reflective state. Inthis state, particles 116 are moved under influence of applied voltageto rear electrode 110 such that TIR can occur at sheet 102. The TIReffect is illustrated by directional light rays 128 and 132 emitted bythe front light source in a direction perpendicular to sheet 102. Thelight rays are totally internally reflected in a semi-retro-reflectivemanner instead of a Lambertian manner back towards the viewer 124 asillustrated by light rays 130 and 134, respectively, centered about a30° half angle cone.

The right side of dotted line 126 depicts a portion (or pixel) ofdisplay 100 in the frustrated TIR dark state. In this state,electrophoretically mobile particles 116 are moved under the influenceof an applied voltage of opposite polarity—as compared to the appliedvoltage on the left side of FIG. 2—near the surface of the transparentfront electrode 106 such that TIR is frustrated. This is illustrated bydirectionally emitted light rays 136 and 138 being absorbed, forexample, by particles 116 which are light absorbing.

FIG. 3 is a close-up view of the extractor elements 122 in light guide120 of display 100 of FIG. 2. Specifically, FIG. 3 shows light source118, light guide 120 and extractor elements 122. Extractor elements arestructures within the light guide to extract light from said guide in acontrollable manner. There are many ways to extract light from lightguides. The depiction in FIG. 3 simply illustrates the concept.

FIG. 3 also shows a plurality of light rays 150 from light source 118being reflected and re-directed into a respective plurality of reflectedlight rays 152 in a direction perpendicular to the semi-retro-reflectivesurface. The light rays are emitted and re-directed in a perpendiculardirection within a non-Lambertian narrow angular range towards thesemi-retro-reflective sheet.

FIG. 4 shows an exemplary display according to another embodiment of thedisclosure.

Specifically, FIG. 4 shows a portion of a frustratable TIR displayequipped with a directional front light and cross-walls. Display 200 ofFIG. 4 includes a semi-retro-reflective outer sheet 202 having aplurality of convex protrusions in the shape of hemi-spherical beads 204facing viewer 218, transparent front electrode 206 on a surface of thehemispherical beaded surface, rear support 208 comprising of topconductive layer 210 acting as rear electrode in TFT or patternedelectrode array, an optically clear, inert, low refractive index medium214. Medium 214 fills the cavity formed between front transparentelectrode 206 and rear electrode 210. Medium, 214 receives suspendedlight absorbing electrophoretically mobile particles 216.

Voltage source 212 connects front 206 and rear electrodes 210. Frontlight source 220 illuminates a surface of display 200. Light guide 222and extractor elements 224 re-direct the light in a perpendiculardirection towards semi-retro-reflective sheet 202.

Display 200 further comprises walls 226 which form wells or compartmentsfor confining mobile particles 216. The walls or cross walls 226 may beconfigured to create wells or compartments in a variety of shapes. Forexample, the wells may be square-like, triangular, pentagonal, hexagonalor a combination thereof. Walls 226 may include a polymeric material andpatterned by such techniques as photolithography, embossing or molding.Walls 226 help to confine the electrophoretically mobile particles 216to prevent settling and migration of particles 216 which may lead topoor display performance over time.

Single or multiple pixels may be switched within the wells orcompartments formed by the cross walls 226 as further shown in FIG. 4.For example, light rays 228 and 230 may be emitted by the front lightsource directionally in a perpendicular direction within a narrowangular range (i.e., non-Lambertian) toward semi-retro-reflective sheet202. The light rays may undergo TIR and may be reflected as reflectedrays 232 and 234, respectively, back toward viewer 218. The reflectionsubstantially preserves the non-Lambertian characteristic of the lightoutput of the directional front light to create a light or reflectivestate. This is made possible when voltage is applied such that particles216 are moved and collected at rear electrode surface 210.

Alternatively, the polarity of the applied voltage may be reversed andparticles 216 may move from rear electrode 210, toward transparent frontelectrode surface 206 such that light rays 236 and 238 are absorbed orscattered by particles 216 at single or multiple pixels. The pixels maybe located within the compartments or wells created by cross walls 226to create a dark state.

FIG. 5 illustrates another embodiment of the disclosure havingperforated sheet. Here, instead of light being reflected at asemi-retro-reflective front sheet (e.g., FIGS. 2 and 4), light isreflected at a semi-specular or semi-retro-reflective surface on aperforated sheet or film. Display 300 includes transparent outer sheet302. Sheet 302 may be optional and light guide 330 may be used as theonly outer sheet. Display 330 also includes rear support 304 with topconductive layer 316 acting as rear electrode 306 which may include aTFT or a patterned array.

Disposed within a cavity formed between outer sheet 302 and rearelectrode 306 is a thin, perforated, continuous (represented by thedotted lines 310) sheet or film 308. Sheet 308 may be formed of a tracketched polymeric material such as polycarbonate, polyester, polyimide orsome other polymeric material or glass with a thickness of at leastabout 10 microns. The perforated nature of film 308 allows lightabsorbing, electrophoretically mobile particles 312 to pass throughperforations 314. An average diameter of the perforations in sheet 308may be greater (e.g., about 10 times greater) than the average diameterof particles 312. The perforations in sheet 308 may constitutesufficiently large fraction (e.g., at least 10%) of the total surfacearea of membrane 308 to permit substantially unimpeded passage ofparticles 312 through perforations 314 of sheet 308.

Display 300 in FIG. 5 further shows an additional first perforated andcontinuous (represented by the dotted lines 318) conductive layer 316acting as a front electrode on top of the perforated, continuous(represented by the dotted lines 310) film or sheet 308. The film orsheet may define a membrane. Perforations may also define pores orapertures. Layer 316 may include a transparent conductive material suchas indium tin oxide (ITO) or Baytron™. In one embodiment, layer 316includes a thin, light reflective, metal layer such as aluminum, silver,gold, aluminized Mylar™ flexible film or other conductive material toenhance reflectance. Reflective layer 316 may be assembled by coatingsurface 308 with a reflective (e.g., aluminum, silver, gold) metallicfilm using conventional vapor deposition techniques.

A second perforated and continuous (represented by the dotted lines 322)layer 320 may be formed on top of layer 316. Second layer 320 mayinclude a semi-retro-reflective coating 320. The semi-retro-reflectivecoating 320 may be comprised of corner-cube or partial corner-cubereflectors or glass beads embedded in a reflective substrate such as thereflective front electrode 316 or in a transparent matrix and backed bythe reflective front electrode 316.

In one embodiment, the diffuse reflectance level fromsemi-retro-reflective coating 320 is not so high as to cause pixel orsub-pixel cross-talk. For example, if light enters through one sub-pixelit should be reflected by semi-retro-reflective coating 320 such thatlight exits through the same sub-pixel, otherwise the contrast and/orcolor saturation will be reduced. The cavity formed by front transparentsheet 302 and rear electrode 306 along with the perforations of theperforated sheet is filled with an optically clear and inert medium inwhich particles 312 are suspended.

Voltage source 326 may apply a bias between the conductive first layer316 on perforated film 308 and rear electrode 306. In conventionaldisplay architectures where a reflective metal perforated layer or filmis interposed between two electrode surfaces (i.e., top and bottomelectrodes), the metal film is an equipotential surface which isuncontrolled and can take any value of voltage between the voltages inthe top and bottom electrodes. The precise voltage depends on the chargedistribution across the entire cell. Having a variable voltage on anunconnected electrode means that the cell performance will have variableoperation speeds and hysteresis. Experimental data shows that such anarchitecture renders the device inoperable. One solution to theconventional architecture's shortcomings is to electrically connect thereflective perforated metal layer to the rear electrode such that saidreflective perforated metal layer becomes the front electrode layer asdescribed in the disclosed embodiments.

Display 300 further comprises directional front light source 328, atransparent light guide 330 and light extractor elements 332. Lightextractor 332 redirects emitted light from light source 328 in theperpendicular direction in a narrow angular range towards the reflectivelayer 320 on the perforated film surface.

In the light state, the light is reflected back in a narrow angularrange back to viewer 334. This is depicted on the left-hand side ofdotted line 336. Here, a voltage bias of the correct polarity has beenapplied such that electrophoretically mobile particles 312 move throughperforations 314 of the perforated sheet (and conductive and reflectivelayers) toward rear electrode 306 such that particles collect at thesurface thereof. When particles 312 are positioned behind perforatedsheet 308, a light state is created. Light ray 338 emitted in theperpendicular direction from the light guide 330 is reflected at thesemi-retro-reflective surface 320 back toward viewer 334 such that thereflected light (represented by reflected light ray 340) preserves thenon-Lambertian characteristic of the light output to thereby minimizethe amount of light not directed back to the viewer 334.

On the right-hand side of dotted line 336, FIG. 5 shows a dark statesuch that particles 312 are moved through the perforations 314 under theinfluence of a voltage bias of opposite polarity. In this state,particles 312 collect at the surface of the semi-retro-reflective layer320 so as to absorb light rays emitted from the light guide 330. This isrepresented by light rays 342 being absorbed by particles 312.

Display 300 may further comprise one or more walls as shown in FIG. 4.Each well may create a compartment to confine the electrophoreticallymobile particles 312 in display 300. The walls or cross walls may bedesigned so as to create wells or compartments in any of the shapesdiscussed above. The walls may be formed of polymeric material and maybe patterned by such techniques as conventional photolithography,embossing or molding. The walls help confine particles 312 and preventsettling and migration of particles 312 which leads to poor displayperformance over time.

Another embodiment of a reflective display with a directional frontlight is shown in display 400 of FIG. 6. Display 400 includes anoptional transparent front sheet 402, rear support 404, rear electrode406 in a TFT or patterned array, a perforated, continuous (representedby the dotted lines 410) sheet or film 408, and electrophoreticallymobile particles 412 suspended in an optically clear, inert medium 414.

An additional specularly reflective, conductive perforated (representedby the dotted lines 418 to imply a continuous layer) layer 416 is addedon top of the perforated sheet such that the reflective conductive layerfaces transparent outer sheet 402 to act as a front electrode.Reflective layer 416 may define a thin light reflective metal layer suchas aluminum, silver, gold, aluminized Mylar™ flexible film or othersimilar material. Reflective layer 416 may be assembled by coatingsurface 408 with a reflective (e.g., aluminum, silver, gold) metallicfilm using standard vapor deposition techniques. Display 400 furthercomprises a voltage source 420 to apply voltage bias across the frontand rear electrodes to move the electrophoretically mobile particles412. The exemplary embodiment of FIG. 6 also includes directional frontlight system comprising light source 422 and transparent light guide 424equipped with light extractor elements 426. On top of the light guidesurface and disposed between the light guide 424 and viewer 428 is lightdiffusing layer 430. There are a number of possibilities for thematerials of construction for light diffusing layer 430 such as ground,grey-eyed or opal glass diffusers and Teflon™ or other conventionalpolymeric diffusers.

The embodiment of display 400 operates, for example, in the followingmanner. On the left side of the dotted line 432, electrophoreticallymobile particles are moved through perforations 434 to rear electrodesurface 406 under an applied voltage. Light rays 436 that are emitteddirectionally from front light guide 424 in a perpendicular directionare reflected in a specular manner as shown by reflected light ray 438by the reflective and conductive layer 416 on top of the perforatedsheet or film 408 such that the reflected light substantially maintainsand preserves the non-Lambertian characteristics of light output fromfront light guide 424.

As the light ray escapes the display and back to the viewer 428 throughtransparent light guide 424, light ray 438 passes through the outertransparent light diffuser sheet 430 in order to soften or whiten thelight so that the light state of the display appears paper-like. Thedegree of softening can be controlled by the characteristics of thelight diffuser layer and requirements of the application.

On the right side of the dotted line 432, the mobile particles 412 aremoved through perforations 434 to a top surface of reflective electrode416 such that directional light rays emitted by the front light sourceare absorbed thereby. This creates a dark state and is shown by lightrays 440 emitted by the front light source which are absorbed by theelectrophoretically mobile particles 412.

Display 400 may further comprise walls as illustrated in display 200 inFIG. 4. The walls create wells or compartments that confineelectrophoretically mobile particles 412. The walls help confine mobileparticles 412 to prevent settling and migration of particles 412 whichleads to poor display performance.

FIG. 7 illustrates an exemplary embodiment of the disclosure having aperforated sheet with a reflective layer. Display 500 of FIG. 7 issimilar in construction to display 400 of FIG. 6. Display 500 includesan optional transparent outer sheet 502, rear support 504, rearelectrode 506 that may be a TFT or patterned array, perforated andcontinuous (represented by the dotted lines 510) sheet or film 508 withperforations, pores or apertures 512, optically clear and inert medium514 filling the cavity formed between transparent outer sheet 502 (thesheet may be optional as the light guide may be used as a transparentouter sheet) and rear electrode 506 and contained within theperforations 512.

Display 500 also includes front light source 516, transparent lightguide 518 equipped with array of light extractor elements 520 andtransparent light diffuser sheet 522 located on top of transparent lightguide 518 and facing viewer 524. Display 500 further comprises a firstperforated, continuous (represented by the dotted lines 528) reflectivelayer 526 on perforated sheet 508. On top of perforated reflective layer526 is a second transparent conductive, perforated and continuous(represented by the dotted lines 532) layer 530. This layer 530 acts asfront electrode and may be constructed from ITO or Baytron™ ornanoparticles such as nanometallic wires dispersed in a polymer matrixor a combination thereof. Display 500 further comprises voltage source534 for applying a bias for moving electrophoretically mobile particles517.

In an exemplary embodiment, display 500 operates in the followingmanner. On the left-hand side of dotted line 536, particles 517 aremoved through perforations 512 to rear electrode surface 506 under anapplied voltage bias. Light rays depicted by ray 538 are emitteddirectionally by the light guide 518 in a perpendicular direction. Thelight rays pass through transparent conductive layer 530 which acts asthe front electrode. The light rays are reflected in a specular manneras shown by reflected light ray 540 by the reflective layer 526 on topof the perforated sheet or film 508 such that the reflected lightsubstantially maintains and preserves the non-Lambertian characteristicof the light output from the front light source. As reflected light ray540 escapes display 500 back to the viewer 524 through the transparentlight guide 518, the light ray passes through the outer transparentlight diffuser sheet 522 in order to soften or whiten the light suchthat the light state of the display appears paper-like. The degree ofsoftening may be controlled by the characteristics of light diffuserlayer 522 and the display requirements.

On the right side of the dotted line 524, the electrophoretically mobileparticles 517 are moved through perforations 512 to a top surface oftransparent front electrode 530 such that directional light rays emittedby the light guide are absorbed by the particles. This creates a darkstate as shown by light rays 542 emitted by the light guide and absorbedby particles 517.

While not shown, display 500 may further comprise walls as discussed inrelation to FIG. 4. The walls (not shown) create wells or compartmentsto confine mobile particles 517 in the display. The walls help confinemobile particles 517 to prevent settling and migration of particles 517which leads to poor display performance.

The disclosed embodiments may be used in such applications electronicbook readers, portable computers, tablet computers, cellular telephones,smart cards, signs, watches, wearables, shelf labels, flash drives andoutdoor billboards or outdoor signs comprising a display.

While the principles of the disclosure have been illustrated in relationto the exemplary embodiments shown herein, the principles of thedisclosure are not limited thereto and include any modification,variation or permutation thereof.

what is claimed is:
 1. A reflective display device, comprising: asemi-retro-reflective display sheet having one or more convexprotrusions that reflects light in a narrow angle relative to thedirection of the incident light; a light source to emit light in aperpendicular direction towards the display sheet; a front electrode; arear electrode; a fluid disposed between the front and the rearelectrodes; a plurality of electrophoretically mobile particlessuspended in the optically transparent fluid; and a voltages source incommunication to the front and the rear electrodes to selectively movethe electrophoretically mobile particles in the fluid.
 2. The display ofclaim 1, wherein the light source defines a light emitting diode (LED),cold cathode fluorescent lamp (CCFL) or a surface mount technology (SMT)incandescent lamp.
 3. The display of claim 1, wherein the frontelectrode is transparent and disposed on the semi-retro-reflectivedisplay sheet.
 4. The display of claim 1, wherein the rear electrodefurther comprises a thin film transistor or driven patterned array. 5.The display of claim 1, wherein the fluid defines an opticallytransparent fluid a refractive index lower than an index of refractionof the semi-retro-reflective display sheet.
 6. The display of claim 1,wherein the voltage source provides: a first voltage to movesubstantially all of the electrophoretically mobile particles toward therear electrode to allow incident rays to be internally reflected at thesemi-retro-reflective display sheet towards the viewer; and a secondvoltage to move substantially all of the electrophoretically mobileparticles toward the front electrode and collect at thesemi-retro-reflective surface to thereby frustrate total internalreflection.
 7. The display of claim 1, further comprising one or morecross walls.
 8. The display of claim 1, wherein the front light and thesemi-retro-reflective display sheet are arranged relative to each otherto provide a substantially non-Lambertian light display.
 9. The displayof claim 1, wherein the narrow angle defines an angle in the range ofabout 10° to about 30°.
 10. A reflective display, comprising: atransparent outer sheet; a light source to emit light in a perpendiculardirection towards the transparent outer sheet; a rear electrode; aperforated sheet situated between the light source and the rearelectrode; a front electrode disposed over the perforated sheet; asemi-retro-reflective surface over the perforated sheet; a mediumdisposed within the cavity formed between the transparent outer sheetand the rear electrode; a plurality of electrophoretically mobileparticles suspended in the medium; and a voltages source incommunication to the front and the rear electrodes to selectively movethe electrophoretically mobile particles in the fluid.
 11. The displayof claim 10, further comprising one or more cross walls.
 12. The displayof claim 10, wherein the light source and the semi-retro-reflectivesurface are arranged relative to each other to provide a substantiallynon-Lambertian light display.
 13. The display of claim 10, wherein therear electrode further comprises a thin film transistor or drivenpatterned array.
 14. The display of claim 10, wherein the voltage sourceprovides: a first voltage to move substantially all of theelectrophoretically mobile particles toward the rear electrode to allowincident rays to be reflected at the semi-retro-reflective display sheettowards the viewer; and a second voltage to move substantially all ofthe electrophoretically mobile particles toward the front electrode andcollect at the semi-retro-reflective surface to thereby absorb incidentrays.
 15. A reflective display, comprising: a transparent outer sheet; alight source to emit light in a perpendicular direction towards thetransparent outer sheet; a rear electrode; a perforated sheet situatedbetween the light source and the rear electrode; a reflective layerdisposed over the perforated sheet; a transparent front electrodedisposed over the perforated sheet; a medium disposed within the cavityformed between the transparent outer sheet and the rear electrode; aplurality of electrophoretically mobile particles suspended in themedium; and a voltages source in communication to the front and the rearelectrodes to selectively move the electrophoretically mobile particlesin the fluid.
 16. The display of claim 15, further comprising one ormore cross walls.
 17. The display of claim 15, wherein the light sourceand the semi-retro-reflective surface are arranged relative to eachother to provide a substantially non-Lambertian light display.
 18. Thedisplay of claim 15, wherein the rear electrode further comprises a thinfilm transistor or driven patterned array.
 19. The display of claim 15,wherein the transparent front electrode is comprised of ITO or Baytron™or electrically conductive particles dispersed in a polymer matrix or acombination thereof.
 20. The display of claim 15, wherein the voltagesource provides: a first voltage to move substantially all of theelectrophoretically mobile particles toward the rear electrode to allowincident rays to be reflected at the semi-retro-reflective display sheettowards the viewer; and a second voltage to move substantially all ofthe electrophoretically mobile particles toward the front electrode andcollect at the semi-retro-reflective surface to thereby absorb incidentrays.